The disclosure relates to a hydrostatic drive, in particular a fan drive.
A coolant circuit of an engine, for example of an internal combustion engine, can be driven by means of a fan drive of this type.
U.S. Pat. No. 5,875,630 discloses a fan drive in which a hydraulic motor of the fan is driven via a variable displacement pump. The variable displacement pump, in its basic position, is set toward the maximum feed volume flow and can be adjusted toward minimizing the feed volume flow via single-edge control with a fixed throttle and an adjusting throttle. The disadvantage of this solution is that, on the one hand, a high outlay in terms of the adjustment of the variable displacement pump is required and, on the other hand, the fan can be actuated in only one direction.
U.S. Pat. No. 6,179,570 B1 discloses a similar fan drive in which the adjustment of the variable displacement pump toward a reduction in the feed volume can be adjusted via an electroproportionally adjustable pressure regulating valve (DRE), the control oil being picked off from the pressure medium volume flow to the hydraulic motor.
In this drive, too, only one direction of rotation of the hydraulic motor is provided. Another disadvantage is the internal control oil pick-off, since this is subject to comparatively high fluctuations.
U.S. Pat. No. 6,684,636 B2 discloses a generic hydrostatic drive with a variable displacement pump which is pivotable through zero and drives a hydraulic motor, the drive torque of which is reversible. The variable displacement pump is adjusted via an actuating cylinder which is prestressed toward the minimum feed volume flow. In a similar way to the prior art described above, the actuating cylinder is adjusted toward a higher feed volume flow via an electroproportionally adjustable pressure regulating valve with external control oil supply. If, then, the hydraulic motor is used for driving a fan, in the event of a power failure in the control electronics, the variable displacement pump pivots back to zero, and therefore, correspondingly, the fan is no longer driven, and then overheating of the coolant and consequently engine damage may occur.
By contrast, the object on which the disclosure is based is to provide a hydrostatic drive, in particular a fan drive, with improved operating reliability.
This object is achieved by means of a hydrostatic drive having the features set forth herein.
Advantageous developments of the disclosure are set forth herein.